While the present invention of endless belt support, operation, installation and removal can be effectively used in a plurality of different belt configurations, it will be described for clarity as used as an intermediate transfer belt (ITB) in electrostatic marking systems such as electrophotography or xerography. It is to be appreciated that for other electrophotographic applications the invention can be applied to photoreceptor belts and media transport belts. It is to be further appreciated that the invention can be applied to systems using other marking technologies, including ink jet, solid ink, offset, dye sublimation technologies to the extent that systems can be constructed in the same modular fashion as described here.
It is advantageous for future marking systems to become modular in construction. This has been the focus of present research. It is well known that benefits of a modular marking system are broad market and application coverage by assembling different systems from a core set of modules (i.e., monochrome, highlight color, 4-color, 6-color, etc. systems), and reduced manufacturing costs and field service costs due to economies of increased volumes of a small set of core modules. In this invention, it is assumed there is a base marking module capable of creating at least a single color separation. A printing system is constructed from 1 to N of these marking modules along with supporting input and output modules. For current printing systems, the value of N may be 6 or 7, however there is utility in systems that can achieve N of 8. From both a technical and financial perspective, a “global” belt transport, either sheet transport, photoreceptor, or ITB, is clearly advantaged over having modular transports within each marking module. Such a global belt is required to span from the input module, across each marking module, and the output module. Historically, such belt transports require purpose-built belt modules that cannot be readily modularized. The dilemma is to provide all the advantages of a global belt transport while still retaining the essential modularity desired for future marking apparatus.
By way of background, in marking systems such as xerography or other electrostatographic processes, a uniform electrostatic charge is placed upon a photoreceptor belt or drum surface. The charged surface is then exposed to a light image of an original to selectively dissipate the charge to form a latent electrostatic image of the original. The latent image is developed by depositing finely divided and charged particles of toner upon the belt or drum photoreceptor surface. The toner may be in dry powder form or suspended in a liquid carrier. The charged toner, being electrostatically attached to the latent electrostatic image areas, creates a visible replica of the original. The developed image is then usually transferred from the photoreceptor surface to an intermediate transfer belt (ITB) or to a final media such as paper.
In some of these electrostatic marking systems, a photoreceptor belt, an intermediate transfer belt (ITB), or a media transport belt is generally arranged to move in an endless path through the various processing stations of the xerographic marking process. In this endless path, several xerographic-related stations are traversed by the belt which becomes abraded and worn. Since the belt is used continuously, the surfaces of the belt may be constantly abraded and cleaned by a blade and/or brushes and prepared to be used once again in the marking process. The belt may be exposed to friction or heat and moved by rollers that provide the belt movement to accomplish the belt purpose. There is further the possibility of damaging the belt surface or edge from extrinsic sources such as inadvertent contact by the machine operator or service technician. Therefore, generally, after a period of operation, especially in high speed color systems, the belt needs to be replaced.
Image-carrying belts used in color printing processes can be especially difficult to replace and install. In some machines for example, the intermediate transfer belt is over 6-10 feet long and travels past a plurality of marking stations. Belt installation requires careful alignment between the belt rollers to prevent belt and other machine component damage. In a scalable modular printing system, even longer belt lengths may be required, and the belt replacement or removal operation is increasingly difficult without belt damage occurring.
Even in monochromatic marking systems that use shorter belts for various functions, extreme care must be taken not to damage the belts during installation. In some instances, the belts are constructed of thin flexible polymeric materials that can easily scratch or be damaged during belt replacement or even during original installation. Photoreceptor, ITB, and media transport belts are generally supported within a printing system by a belt module. The belt module is comprised of an integral frame assembly which supports multiple rollers. The rollers provide drive force, tensioning, steering, stabilization, and other functions to support and operate the belt. Generally, the belt module resides within the interior of the belt, that is, it occupies the volume defined by the periphery of the interior surface of the belt. Thus, there exists a substantial frame structure internal to the belt which is carefully designed to support the specific length of the belt. The frame structure is further designed to provide accurate location of rollers and resist deformation due to external loads. Most commonly, belts are installed onto a belt module by sliding the belt over the outside periphery of the belt module. The direction of belt installation is thus perpendicular to the direction of belt travel during operation. It is generally not possible to design stationary frame members that would obstruct any portion of the belt module periphery. Thus, although the existence of the belt module provides a stable support for the belt, it also places design constraints upon the system frame design, in particular the need for unobstructed access to at least one side of the belt module. This consideration, together with the previously cited concerns, points to a need for an improved method of support, operation, installation, and removal of global belts within a modular scalable printing system.